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Google has released its latest monthly security update for Android devices, including a serious bug in some Broadcom Wi-Fi chipsets that affects millions of Android devices, as well as some iPhone models.

Dubbed BroadPwn, the critical remote code execution vulnerability resides in Broadcom's BCM43xx family of WiFi chipsets, which can be triggered remotely without user interaction, allows a remote attacker to execute malicious code on targeted Android devices with kernel privileges.

"The most severe vulnerability in this [runtime] section could enable a remote attacker using a specially crafted file to execute arbitrary code within the context of an unprivileged process," Google describes in the July 2017 Android Security Bulletin.

Since Artenstein will be presenting his finding at Black Hat 2017 event, details about the BroadPwn bug is scarce at this moment.

"The Broadcom BCM43xx family of Wi-Fi chips is found in an extraordinarily wide range of mobile devices – from various iPhone models to HTC, LG, Nexus and practically the full range of Samsung flagship devices," the abstract for Artenstein's talk says.

Besides the fix for the BroadPwn vulnerability, July's Android Security Bulletin includes patches for 10 critical, which are all remote code execution bugs, 94 high and 32 moderate rated vulnerabilities.

Two months ago, an over-the-air hijacking vulnerability was discovered in Broadcom WiFi SoC (Software-on-Chip) chips, allowing attackers within the same WiFi network to remotely hack, iPhones, iPads, iPods and Android handsets without any user interaction.

At that time, Apple rushed out an emergency iOS patch update to address the serious bug, and Google addressed the flaw in its Android April 2017 security updates.

Android Security Bulletin: July 2017 Updates

Among the other critical flaws is a long list of vulnerabilities in the Mediaserver process in the Android operating system, which also allows attackers to perform remote code execution on the affected devices.

One of the vulnerabilities is an issue with the way the framework handles some specific files. The libhevc library has an input validation vulnerability (CVE-2017-0540), which can be exploited using a crafted file.

"A remote code execution vulnerability in libhevc in Mediaserver could enable an attacker using a specially crafted file to cause memory corruption during media file and data processing," the vulnerability description says.

"This issue is rated as Critical due to the possibility of remote code execution within the context of the Mediaserver process."

The over-the-air updates and firmware for Google devices have already been issued by the company for its Pixel and Nexus devices, though rest of Android still need to wait for an update from their OEMs, leaving million of Android devices vulnerable for next few months.

Millions of smartphones and smart gadgets, including Apple iOS and many Android handsets from various manufacturers, equipped with Broadcom Wifi chips are vulnerable to over-the-air hijacking without any user interaction.

Just yesterday, Apple rushed out an emergency iOS 10.3.1 patch update to address a serious bug that could allow an attacker within same Wifi network to remotely execute malicious code on the Broadcom WiFi SoC (Software-on-Chip) used in iPhones, iPads, and iPods.

The vulnerability was described as the stack buffer overflow issue and was discovered by Google's Project Zero staffer Gal Beniamini, who today detailed his research on a lengthy blog post, saying the flaw affects not only Apple but all those devices using Broadcom's Wi-Fi stack.

Beniamini says this stack buffer overflow issue in the Broadcom firmware code could lead to remote code execution vulnerability, allowing an attacker in the smartphone's WiFi range to send and execute code on the device.

Attackers with high skills can also deploy malicious code to take full control over the victim's device and install malicious apps, like banking Trojans, ransomware, and adware, without the victim's knowledge.

In his next blog post that's already on its way, Beniamini will explain how attackers can use their assumed control of the Wi-Fi SoC in order to further escalate their privileges into the application processor, taking over the host’s operating system.

Over-the-Air Broadcom Wi-Fi SoC Hack

According to the researcher, the firmware running on Broadcom WiFi SoC can be tricked into overrunning its stack buffers, which allowed him to send carefully crafted WiFi frames, with abnormal values, to the Wi-Fi controller in order to overflow the firmware's stack.

Beniamini then combined this value with the frequent timer firings of the chipset to gradually overwrite specific chunks of device's memory (RAM) until his malicious code is executed.

So, to exploit the flaw, an attacker needs to be within the WiFi range of the affected device to silently take over it.

"While the firmware implementation on the Wi-Fi SoC is incredibly complex, it still lags behind in terms of security," Beniamini explains. "Specifically, it lacks all basic exploit mitigations – including stack cookies, safe unlinking and access permission protection."

The researcher also detailed a proof-of-concept Wi-Fi remote code execution exploit in the blog post and successfully performed it on a then-fully updated (now fixed) Nexus 6P, running Android 7.1.1 version NUF26K – the latest available Nexus device at the time of testing in February.

The flaw is one of the several vulnerabilities discovered by Beniamini in the firmware version 6.37.34.40 of Broadcom Wi-Fi chips.

Security Patch for Nexus & iOS Released; Others Have to Wait!

Google Project Zero team reported the issue to Broadcom in December. Since the flaw is in Broadcom's code, smartphone makers had to wait for a patch from the chip vendor before testing the patch and pushing it out to their own user base.